JP2788907B2 - Linear drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear drive for a belt emergency tightening device, the drive comprising a cylindrical tube and a piston adapted to slide therein, the hollow internal space being provided. A linear drive having an end wall at one axial end and an explosive drive charge, which, when ignited, exposes the interior space of the piston to gas under pressure. Things.

[0002]

BACKGROUND OF THE INVENTION A linear drive of this type is disclosed in DE-A-44 15 10
9. The drive load is ignited in an emergency,
Under the action of the evolved gas, the piston performs a tightening stroke, which is converted via a belt emergency tightening device into a rotational movement in the belt winding direction of the belt drum of the belt retractor. Thus, so-called belt slack is removed from the belt system, so that the vehicle occupant can take part in the deceleration of the vehicle from the earliest possible point of the accident.

[0003] One problem with such a linear drive is that the drive load can be ignited under adverse conditions, for example, in the event of misuse, ie, a vehicle fire may occur. In the event of overheating or the vehicle occupant is already displacing forward, the dangers due to the drive load and the linear drive must be eliminated. DE-A-44 15 10
No. 9 discloses a method of constructing a cylindrical tube so that the tube is less likely to burst, and thus, in the worst case, the danger caused by the driving load can be prevented. Such a structure, however, must take the risk of increasing weight.

[0004]

SUMMARY OF THE INVENTION One object of the present invention is to develop a linear drive of the type mentioned at the outset to reduce the weight of the linear drive while ensuring that the cylindrical tube does not burst. It is to ensure safety.

[0005]

For this purpose, a linear drive of the type described initially has a passage opening at its end wall, which opening is provided on the inner space side by a blow-off or blow-through patch. It has the characteristic of being closed. Such a blow-through patch opens the passage opening so that such pressure is released from the inner space of the piston when excessive pressure is generated in the inner space of the piston, so that the cylindrical tube does not particularly need to be solidly configured. Can also prevent the rupture of the tube. By appropriately selecting the dimensions of the atrium patch,
The maximum pressure obtained in the space inside the piston can be set to suit the respective conditions.

[0006] The linear drive is further calibrated.
A discharge opening is provided in the atrium patch, and the discharge opening
Connect the inner space of the ston to the passage opening in the equipment end wall
In. According to this configuration, in addition to restricting the maximum pressure generated in the inner space of the piston, the belt is connected to an energy absorbing means such as a torsion rod adapted to absorb a peak load generated in the belt system. When the drum is connected, several advantages are obtained for the linear drive after an emergency tightening of the belt. Such an energy absorbing means is described in DE-A-42 27 781. After the emergency belt tightening is completely completed,
That is, after the piston has completed the tightening stroke after ignition of the drive charge and the belt drum rotates in the unwinding direction due to the action of the energy absorbing means, the belt drum is connected to the linear drive. Thus, the piston of the linear drive will make a reversing movement towards its initial position. There is a discharge opening when the piston reverses in the internal space of the cylindrical tube
Therefore, the gas pressure is not induced by the reversing motion . Emissions openings also result in the loss of pressure during the stroke tightening piston. However, since the reversing motion of the piston is performed much more slowly than the tightening stroke, it is sufficient to provide a relatively small discharge opening to exhaust the internal space of the piston during this reversing motion. The pressure loss during the rapid tightening movement of is small.
Furthermore, such pressure losses can be compensated for by providing a larger drive charge .

According to another preferred feature of the invention, the atrium patch is pressed into the interior space. In this way, a particularly reliable placement of the blow-through patch in the interior space of the piston is obtained.

[0008] As an alternative to the construction of the press-fitted atrium patch, the patch may be provided with a tubular mounting skirt that extends through the passage opening so that the atrium patch is firmly attached to the end wall through the folded edge. It is possible to install. Thus, it becomes possible to securely attach the atrium patch to the end wall.

According to another preferred embodiment of the invention, the blow-through patch extends through the passage opening and has a connecting part connected with a tear-off part which meshes with the inner wall surface of the cylindrical tube. Such a tear-off component is displaceable in a cylindrical tube in a direction that follows the direction of movement of the piston upon ignition of the drive charge, while upon movement of the piston in the opposite direction. Locked in the cylindrical tube, as the piston attempts to move further, the connecting piece is torn from the blow-through patch and the passage opening is opened. With such a structure, when the piston reverses to the initial position after the tightening stroke occurs, the same effect as that obtained by the calibrated opening in the blow-by patch is obtained. However, in this embodiment, no loss occurs during the tightening stroke.

[0010] Preferably, the blow-by patch is made of metal foil. This leads to a high reproducibility of the value of the pressure at which the passage opening opens. This is because such metal foils can be manufactured with tight tolerances and the maximum pressure they carry is largely unaffected by temperature changes.

[0011]

Next, the present invention will be described with reference to the drawings. 1 shows a linear drive 10 according to the invention and an associated belt emergency tightening device 12.
And the belt retractor 14, wherein the emergency belt tightening device 12 is arranged to act on the belt retractor 14 via a speed increasing gear train 16.

As shown in FIG. 2, the linear drive 10 has a cylindrical tube 20 and a piston 22 adapted to run therein. The piston 22 has a hollow inner space 24 which has an end wall 26 at one axial end and a powder drive charge 28 at the opposite axial end. A seal ring 30 is provided between the cylindrical tube 20 and the piston 22 on the piston. At the lowermost end in FIG.
It is closed by two. The plug 22 carries an electrical ignition contact for igniting the drive load 28. At the opposite end, the cylindrical tube 20 has an opening 3
4 is provided.
The opening 34 serves to evacuate the cylindrical tube 20 during the tightening stroke of the piston 22.

The piston 22 has, on its outer axially extending surface, gear teeth 36 which extend parallel to the piston longitudinal axis and cooperate with the gears of the gear train 16. , The tightening stroke of the piston 22 is converted into a rotational movement. This rotational movement is transmitted as a rotational movement of the belt retractor 14 in the belt winding direction with respect to the belt drum. Such a tightening stroke occurs when the drive charge 28 is ignited. The charge generates a pressurized gas upon ignition, which fills the interior space of the piston, causing displacement of the piston 22 within the cylindrical tube 20. FIG. 3 illustrates the state of the linear drive device after the occurrence of the tightening stroke. For a more detailed description, see the aforementioned DE-A-44 15 109
Please refer to the following documents.

FIG. 4 is an enlarged scale view of the end of the piston 22 having the end wall according to the first embodiment of the present invention. The end wall has a passage opening 40 extending in the longitudinal direction of the piston.
have. A blow-off or blow-through patch 42 is provided on the end wall on the side facing the inside space, and the blow-through patch 42 blocks the passage opening 40.
The blow-through patch 42 is provided with a point 44 of the intended strength, at which point a passage opening 40 opens when a pressure above a predetermined maximum pressure acts on the inner space 24 of the piston 22, and the pressurized gas 22 is configured to be released from the inner space. Thus, in the worst case, for example, when the piston 22 fails in the initial position and the drive load is ignited, the piston 22
No excessively high gas pressure is generated in the interior of the vehicle, which means that the risk of explosion of the linear drive can be prevented.

The blow-by patch 42 is made of a metal foil pressed into the piston. Since the metal foil is used, the reproducibility of the pressure value at which the passage opening 40 is guaranteed to open is increased. This is because such metal foil parts can be manufactured with very small tolerances and are hardly affected by temperature. Furthermore, the use of a blow-through patch made of metal foil means that debris does not scatter when the passage opening is opened.
Since the space in the piston 22 is completely sealed on the one hand by the blow-through patch and on the other hand by the sealing ring 30, the total gas pressure generated by the drive charge is optimally converted into a tightening stroke.

FIG. 5 illustrates, on an enlarged scale, the end of a piston 22 having an end wall according to a second embodiment of the present invention. A blow-through patch 42 made of metal foil is provided with a tubular skirt 50 which extends through the passage opening and whose axial free end is bent over the outside of the end wall. The blow-by patch 42 is thus securely positioned on the end wall 26. In this embodiment, too, the atrium patch 42 is provided with a point 44 with a planned weakness and the piston 22
The passage opening 40 is created when an excessively high pressure is generated in the inner space.

FIG. 6 illustrates, on an enlarged scale, the end of a piston 22 having an end wall according to a third embodiment of the present invention. To a large extent, the blow-by patch 42 is identical to the blow-by patch of FIG. The atrium patch 42 according to the third embodiment has an additional calibrated discharge opening 60. The opening 60 connects the inner space 24 of the piston 22 with the passage opening, and thus the outer space of the piston, and preferably has a diameter on the order of 0.5 mm.
This discharge opening 60 is permanently open. However, since the diameter of the discharge opening 60 is small, the pressure loss during the tightening stroke of the piston 22 is relatively small. Thus, the pressure loss can be compensated for by providing a larger drive charge. The function of the calibrated discharge opening 60 is that when the piston 22 attempts to return to its initial position after the completion of the tightening stroke, the interior of the space 24 of the piston 22 and the cylindrical tube 2
The aim is to make the pressure in the inner space of zero equalizable. Inner space 24 of piston 22 and cylindrical tube 2
Due to the pressure equilibrium between the inner spaces of zero, no gas pressure can be induced in the inner space 24 of the piston 22 and there is a resistance to the reversing movement of the piston 22 to its initial position. . Thus,
Even if the belt drum of the belt retractor is connected to the linear driving device, the belt webbing can be pulled out from the belt drum.

FIGS. 7 and 8 schematically show a piston end with an end wall of a linear drive according to a fourth embodiment of the invention and such a linear drive. The blow-by patch 42 is substantially the same as that of the second embodiment. Instead of a mounting skirt, a mounting part 51 is provided, which engages a tear-off part 70.
The component 70 is provided with a locking projection 72 that meshes with the inner wall surface of the cylindrical tube 20. These locking projections allow for the displacement of the tear-off component 70 in a direction corresponding to the direction in which the piston moves when the drive load is ignited, but when the piston moves in the opposite direction, the tear-off component does not. It is set to lock on a cylindrical tube. This means that as the piston 22 reverses to its initial position after the tightening stroke, the tear-off component 70 remains in the cylindrical tube and the connecting component 51 is torn off from the blow-through patch 42. . When the passage opening 40 is thus open, the piston 22 can return to its initial position without gas pressure being built up in the inner space 24 to resist the reversal movement to its initial position. Compared to the third embodiment, the structure of the linear drive according to the fourth embodiment has a loss of pressure after ignition of the drive charge 28 below the maximum pressure set by the dimensions of the point 44 having the predetermined weakness. The advantage that there is no is obtained. The inner space 24 of the piston 22 is completely sealed on the one hand by the blow-through patch 42 and on the other hand by the sealing ring 30.

[Brief description of the drawings]

FIG. 1 is a schematic view of a linear drive device of the present invention including a belt emergency tightening device and a belt retractor.

FIG. 2 is a sectional view of the linear drive device according to the first embodiment of the present invention at an initial position.

FIG. 3 after the tightening stroke is completed.
Sectional drawing of the linear drive device of FIG.

FIG. 4 can be drawn on an enlarged scale showing a part of the linear drive of FIG. 2;

FIG. 5 is an elevational view corresponding to FIG. 4 of a second embodiment of the present invention.

FIG. 6 is a view corresponding to FIG. 4 of a third embodiment of the present invention.

FIG. 7 shows a fourth embodiment of the present invention in an initial position.
FIG.

FIG. 8 shows a linear drive device according to a fourth embodiment of the present invention;
FIG. 4 is a schematic cross-sectional view after the tightening stroke has been completed and the piston has completed a reversing movement toward its initial position.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Linear drive 20 Cylindrical tube 22 Piston 24 Hollow inner space 28 Explosive drive charge 26 End wall 40 Passage opening 42 Ventilation patch 50 Tubular skirt 51 Connection part 70 Tear-off part 60 Calibrated discharge opening

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-50-31523 (JP, A) JP-A-6-344863 (JP, A) Fully open 491-243131 (JP, U) Really open 1974 135924 (JP, U) Japanese Utility Model 63-154371 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B60R 22/46 PCI (DIALOG)

Claims (5)

(57) [Claims] 1. A linear drive (10) for a belt emergency tightening device comprising a cylindrical tube (20) and a piston (22) adapted to slide therein.
A piston (22) having a hollow inner space (24) and an end wall at one axial end, and a pyrotechnic drive charge (28), the charge being ignited after being ignited
Yes inside space (24) driving device having a charge was that brought as exposed to the gas pressure (28), said end wall (26) of one passage opening (40) of the piston (22) and, the opening is the inner space (2
4), which is closed by a stairwell patch (42), which has a calibrated discharge
An opening (60) is provided, wherein the discharge opening is
Connect the space (24) to the passage opening (40)
Linear drive, characterized in that that. The apparatus according to the claim 1, wherein the blow-patch (42) inside the space (24) indented have ruri near drive in the piston (22). 3. The apparatus according to claim 1, wherein said blow-through patch (42) is provided with a tubular skirt (50), said skirt extending through said passage opening (40). , the the folded edge blow-patch (4
Firmly mounted have ruri <br/> near driving apparatus 2) on the end wall (26). 4. The device according to claim 1, wherein the blow-by patch (42) is provided with a connecting part (51),
Extends the passage opening (40) medium, said being connected to the inner wall surface meshing with tear-off part of the cylindrical tube (20) (70), said tear-off part (70)
, The well in the direction driving charge was (28) of the piston <br/> tons when ignited (20) corresponds to the direction of movement for transposition, the piston (22) moves in the opposite direction the seals lock the cylindrical tube (20) inside the case, the said blow-patch (42) said connection <br/> part (51) when the piston (22) is try to continue further movement Karahiki earlier, that is to to open the passage opening (40)
Linear drive unit. 5. The apparatus according to any one of claims 1 to 4, wherein the blow-patch (42) is a metal
Linear drive device is constituted by manufacturing the foil.